The etiological agents of AIDS are the human immunodeficiency viruses types 1 and 2. These viruses, which share certain clinical and biological characteristics, have major differences, in particular with regard to the ways in which the host is infected. Thus, infection by HIV-2 is more difficult than by HIV-1 (Ancelle R, O Bletry, A C Baglin, F Brun-Vezinet, M A Rey and P Godeau, 1987, Long incubation period for HIV-2 infection. Lancet. 1:688-9; Marlink R, P Kandki, I Thior, K Travers, G Eisen, T Siby, I Traore, C C Hsieh, M C Dia and E H Gueye. 1994. Reduced rate of disease development after HIV-2 infection as compared to HIV-1. Science. 265:1587-90; Adjorlolo-Johnson G, K M De Cock, E Ekpini, K M Vetter, T Sibailly, K Brattegaard, D Yavo, R Doorly, J P Whitaker and L Kestens. 1994. Prospective comparison of mother-to-child transmission of HIV-1 and HIV-2 in Abidjan, Ivory Coast. JAMA. 272:462-6; Marlink, R. 1996. Lessons from the second AIDS virus, HIV-2. AIDS. 10:689-99.), the plasma viral load of individuals infected by HIV-2 is less high and/or lower than that in individuals infected by HIV-1 (Andersson S, H Norrgren, Z da Silva, A Biague, S Bamba, S Kwok, C Christopherson, G Biberfeld, and J Albert. 2000. Plasma viral load in HIV-1 and HIV-2 singly and dually infected individuals in Guinea-Bissau, West Africa: significantly lower plasma virus set point in HIV-2 infection than in HIV-1 infection. Arch. Intern. Med. 160:3286-93; Popper S J, A D Sarr, K U Travers, A Gueye-Ndiaye, S Mboup, M E Essex, and P J Kanki. 1999. Lower human immunodeficiency virus (HIV) type 2 viral load reflects the difference in pathogenicity of HIV-1 and HIV-2. J Infect Dis. 180:1116-21.), and the individuals infected by HIV-2 develop the illness more slowly (Vittinghoff E, S Scheer, P O'Malley, G Colfax, S D Holmberg and S P Buchbinder. 1999. Combination antiretroviral therapy and recent declines in AIDS incidence and mortality. J Infect Dis. 179:717-20; Blanco R, Carrasco, L, and Ventoso, I. 2003. Cell killing by HIV-1 protease. J. Biol. Chem. 278:1086-93; Liu H, Krizek J, and Bretscher A. 1992. Construction of a GAL1-regulated yeast cDNA expression library and its application to the identification of genes whose overexpression causes lethality in yeast. Genetics 132:665-673).
HIV-2 was identified for the first time in West Africa in 1986 (Clavel F, D Guetard, F Brun-Vezinet, S Chamaret, M A Rey, M 0 Santos-Ferreira, A G Laurent, C Dauguet, C Katlama, and C Rouzioux. 1986. Isolation of a new human retrovirus from West African patients with AIDS. Science. 233:343-6). In this region, the prevalence of HIV-2 varies between 1% and 10% (Langley C L, E Benga-De, C W Critchlow, I Ndoye, M D Mbengue-Ly, J Kuypers, G Woto-Gaye, S Mboup, C Bergeron, K K Holmes, and N B Kiviat. 1996. HIV-1, HIV-2, human papillomavirus infection and cervical neoplasia in high-risk African women. AIDS. 10:413-7; Poulsen A G, B Kvinesdal, P Aaby, K Molbak, K Frederiksen, F Dias and E Lauritzen. 1989. Prevalence of and mortality from human immunodeficiency virus type 2 in Bissau, West Africa. Lancet. 1:827-31; Wilkins A, D Ricard, J Todd, H Whittle, F Dias, and A Paulo Da Silva 1993. The epidemiology of HIV infection in a rural area of Guinea-Bissau. AIDS. 7:1119-22). The majority of these cases of infection by HIV-2, outside West Africa, are found in European countries and especially in Portugal where the individuals infected by HIV-2 represent 13% of the population infected by human immunodeficiency viruses (Soriano V, P Gomes, W Heneine, A Holguin, M Doruana, R Antunes, K Mansinho, W M Switzer, C Araujo, V Shanmugam, H Lourenco, J Gonzalez-Lahoz and F Antunes. 2000. Human immunodeficiency virus type 2 (HIV-2) in Portugal: clinical spectrum, circulating subtypes, virus isolation, and plasma viral load. J. Med. Virol. 61:111-6). In France, it has been estimated that 1% of the population infected by HIV is infected by the type 2 virus.
In developed countries, the individuals infected by HIV-1 and/or by HIV-2 are treated by chemical therapy, composed of molecules having an inhibiting activity for one or other of the two viral enzymes: Reverse Transcriptase and Protease.
Moreover, the individuals infected by HIV-1 and/or by HIV-2 are also treated by chemical therapy, composed of molecules having an inhibiting activity for the viral entry process or for the viral enzymes: Reverse Transcriptase, Protease, and Integrase.
Although that treatment has significantly helped to reduce morbidity and mortality caused by HIV infection (Palella F J, Jr, K M Delaney, A C Moorman, M O Loveless, J Fuhrer, G A Satten, D J Aschman and S D Holmberg. 1998. Declining morbidity and mortality among patients with advanced human immunodeficiency virus infection. HIV Outpatient Study Investigators. N. Engl. J. Med. 338:853-60; Vittinghoff E, S Scheer, P O'Malley, G Colfax, S D Holmberg and S P Buchbinder. 1999. Combination antiretroviral therapy and recent declines in AIDs incidence and mortality. J. Infect. Dis. 179:717-20), some cases of therapeutic failure have been observed.
The possibility of amplifying, from the plasma, RNA or cell DNA of the individuals infected by HIV-1 and in therapeutic failure, has made it possible to understand at the molecular level the spontaneous or progressive inefficacy of therapeutic treatments. The determination, in particular, of the nucleic sequence of the two viral enzymes Reverse Transcriptase and Protease has shown the appearance of a certain number of mutations. The results obtained during studies in vitro in which a wild type viral strain (and therefore sensitive to treatments) carried the mutations have clearly demonstrated the implication of these mutations in the resistance of the virus to treatment.
Researchers have therefore done a certain amount of work on these mutations and the resistances that they generate to orient and guide the choice of therapeutic treatment and optimize its efficacy.
Two different technical approaches were developed to orient therapeutic treatments. One consisted of searching only the already known mutations within the nucleic acid sequences coding for the viral proteins and is called the genotyping approach. The other one, that does not need knowledge of the presence of resistant mutations within the viral sequences, consists of testing in a cell based system the inhibition of viral replication in the presence of inhibiting molecules, and is called the phenotyping approach.
Unfortunately, the economic strategies of the laboratories have the majority of the time led to a general lack of interest in the scientific community with regard to the treatment of patients infected by HIV-2 (the populations most affected by HIV-2 being mainly those in developing countries) or have led to unsuitable solutions: treatments, tests and analyses that are too expensive, diagnoses, for example, phenotyping diagnoses that are too lengthy or impossible to implement on site, absence of competent structures in the country concerned, etc.
Thus, the results obtained during the various studies carried out on HIV-2 have not been sufficiently consistent to make it possible to formulate a correlation between a particular mutation of the HIV-2 protease, and a resistance phenotype.
It should be noted that, the progression of the illness being slower in individuals infected by HIV-2 than in those infected by HIV-1, the counting of T CD4 cells and determination of the plasma viral load do not rapidly take account of the emergence of resistant strains in patients under treatment.
There exist at the present time several companies that provide the resistance profile of an HIV strain isolated from an infected patient through phenotyping. Conceptionally the three tests resemble each other and are based on the ability of each protease inhibitor to inhibit the release of an infectious recombinant virus comprising the protease of the virus infecting the patient. The companies are: EUROFINS-Viralliance (France), which produces Phenoscript™, Virco-Johnson & Johnson (Belgium-USA), which produces Antivirogram™, and Monogram Biosciences, ex Virologic (United States), which produces Phenosense™. In the three cases, performing those tests requires significant logistic organization, personnel skilled in molecular biology and virology, and expensive infrastructures of the P3 secure laboratory type (it would appear that a complete profile would currently cost between 800 and 1,000 euros per sample). The delay existing between the time when the biological material arrives at the laboratories and the time when the resistance profile is established varies, for each strain of HIV-1, between two and three weeks.
Under these circumstances, putting on the market a reliable rapid test, for example, a phenotyping test that is simple to implement and inexpensive has become imperative. Such a test would assist treating physicians to monitor the appearance of resistant strains in patients infected by retroviruses, in particular HIV 1 or 2, in particular for deprived populations. Moreover, this test could also be used for a “high speed” and/or “high throughput” research for new molecules having inhibiting activity for the retrovirus protease.